Kids will put just about anything in their mouths, including potentially toxic single-dose laundry detergent gel packs — the small, soft and colorful capsules that tend to draw children’s interest.

Concerned doctors in the U.K. are now calling for improved safety warnings and childproof packaging of liquid laundry and dishwasher detergent capsules after seeing a rise in the number of young children needing hospital care after swallowing or being exposed to them.

In a recent letter published online in the Archives of Disease in Childhood, U.K. doctors reported a cluster of cases in which five kids under age 2 swallowed the small capsules over the previous 18 months. All the children were treated in a hospital in Glasgow, Scotland, and all recovered, but four children required several days of intubation to treat swelling and help them breathe, and one child needed surgery.

Calls to the national poisoning information hotline in the U.K. reached 647 in the past year.

The authors say that the detergent capsules contain strong alkaline cleaning agents that can destroy tissue and cause inflammation and swelling if swallowed. The small packets can also quickly block throats and airways causing choking, and if the tissues of the esophagus erode from exposure to the chemicals, it can be fatal.

Treatment can not only be drastic, but it also requires the use of intensive-care resources and may have a “catastrophic impact on the child and family,” the authors write. “We feel that the increasing trend in liquid detergent capsule ingestion poses a significant public health issue,” they write.

The capsules are continuing to pose a problem for American kids as well. U.S. poison control hotlines have received 2,950 calls about young kids’ exposure to the gel packets this year — 734 calls in August alone — according to CNN. The cases all involved children under age 5; no deaths have been reported.

As New York City Health Department spokeswoman Chanel Caraway told CNN: “It is something new that we’re seeing. … These are basically brand new to the market and once they started hitting the market is when we started seeing (reports of exposures).”